1. Field of the Invention
The invention relates to an apparatus for the precise treatment of powder and particles of an inorganic and an organic industrial chemical, ceramics, medicine, foodstuff and the like as they are mixed or granulated.
2. Description of the Related Art
A variety of types are known in the art for arrangements which treat powder and/or particles. By way of example, FIG. 3 is a perspective view of a typical granulator of the agitation type which has been extensively used in the art. As shown, the granulator comprises an agitation blade assembly 2 centrally disposed on the bottom surface of a vessel 1, which is sealingly closed by a closure 3 as a charge of powder and/or particles is granulated using the assembly 2. The assembly 2 comprises a rotary shaft 2A, and a plurality of blades which are mounted on the top end of the rotary shaft 2A in a radial array and which may range from 3 to 6 in number. These blades are driven for rotation in a horizontal plane while maintaining a given clearance with respect to the bottom surface of the vessel 1 so that the powder and/or particles may be agitated by the blades for the purpose of granulation. More specifically, a motor 4 is located below the vessel 1 and is connected through a pulley mechanism 4A with a reduction gear 4B, which serves to reduce the rotational speed of the motor 4 in a suitable manner so that the agitation blade assembly 2 may be driven at a given rotational speed. A chopper 5 is mounted on the inner peripheral wall of the vessel 1 and is associated with a motor 6 located outside the vessel 1 so as to be driven thereby to rotate at a high speed within the vessel 1 for crushing or disintegrating the powder or particles received in the latter. A discharge port, not shown, is formed in the peripheral wall of the vessel 1 at a position which is diametrically opposite to the chopper 5, and is associated with a chute 7 which is located slightly below the port. A valve 7A is mounted in the discharge out of the vessel 1 and may be opened to discharge grains which are prepared within the vessel 1 through the chute 7.
On the other hand, the closure 3 is formed with a plurality of openings 3A, only one of which is shown in FIG. 3, for connection with accessory units such as a hopper and a pneumatic conveyor, both not shown, which are used to feed the powder and/or particles to each opening 3A. When a plurality of accessory units are connected with the closure 3 in this manner, the weight of the closure 3 increases to present a difficulty to the manual opening/closing of the closure 3 by an operator. To accommodate for this, a counterweight 8 is attached to the closure 3 through an arm 8A, thus allowing the closure 3 to be opened and closed with a relatively small force. A spray nozzle 9 serves to feed a binder into the charge of the powder and/or particles received within the vessel 1.
When the described granulator of the agitation type is used to granulate the powder and/or particles into grains, the vessel 1 is initially closed by the closure 3 and a given charge of powder and/or particles is fed through the hopper. Subsequently, the motors 4 and 6 are set in motion and a binder is fed into the vessel 1 through the spray nozzle 9, whereupon the agitation blade assembly 2 operates to agitate and mix the charge while causing a uniform impregnation of the charge with the binder to promote the granulation process, and the chopper 5 is effective to adjust the grain size. In this manner, the agitation blade assembly 2 cooperates with the chopper 5 to granulate the charge into grains while causing them to roll on the bottom surface of the vessel 1. As grains of a desired grain size are formed, the charge of powder and/or particle continues to find its way into interstices between the grains thus formed, and is sequentially formed into grains in conjunction with the binder action, ultimately converting the entire charge into grains.
Upon completion of the granulation process, the valve 7A is driven to open the discharge port, whereupon the agitation blade assembly 2 is effective to displace the grains formed to the outside of the vessel 1 through the discharge port and the chute 7 in a gradual manner. When all the grains are displaced out of the vessel 1, a fresh charge of powder and/or particles may be fed into the vessel 1 to repeat the granulation process described above. Thus, the conventional granulator mentioned above is operated as a batch type granulator.
A problem with the above granulator resides in the fact that accomplishing the agitation and mixing of the charge of powder and/or particles by the use of the agitation blade assembly 2 results in an insufficient mixing of the charge and a difficulty of achieving an even mixing of the charge when the amount of charge fed into the vessel 1 is increased, thus making it difficult to obtain grains of an even quality. It will also be noted that the agitation blade assembly 2 has a peripheral speed associated with its radially outer end which is different from a peripheral speed associated with its central part, thus producing differential granulation effects between these parts. Thus, if the rotational speed of the agitation blade assembly 2 is determined on the basis of the peripheral speed at the radially outer end, the peripheral speed at the central part will be too low, thus drastically degrading or even prohibiting the granulation effect at this part. Conversely, if the rotational speed of the agitation blade assembly 2 is determined on the basis of the peripheral speed which prevails at the central part, the peripheral speed at the radially outer end will be too high, causing a crushing of grains formed in this region. Thus, the granulator is unable to prepare grains of an even diameter. Because there is a large difference in the peripheral speed between the central part and the radially outer end as mentioned above, and because this difference increases with an increase in the internal diameter of the vessel, a scale-up of the granulator mentioned is substantially inhibited, whereby its capacity to produce grains is limited. To increase the capacity, there must be provided a plurality of these granulators.
An apparatus for the treatment of powder and/or particles also includes a mixer which mixes powders and/or particles. A mixer of the paddle type is known as a typical one of the arrangements which continuously mixes powders and/or particles. A mixer of the paddle type comprises a horizontally elongate vessel, a rotary shaft disposed within and extending longitudinally of the vessel, a plurality of paddles mounted on the rotary shaft at a given interval, and a motor for driving the paddles for rotation through the rotary shaft. A supply port is formed in the upper surface of the elongate vessel at one end thereof while a discharge port is formed in the bottom surface of the vessel at the other end thereof for discharging a resulting mixture.
When powders and/or particles are to be mixed together, a plurality of different powders and/or particles are continuously fed into the vessel through the supply port. The rotating paddles within the vessel displaces them to the discharge port while gradually mixing them, whereby they are continuously displaced through the discharge port as a mixture.
In this instance, the paddles allow an even mixing of the plurality of powders and/or particles, but because the paddles lack the function of crushing the powders and/or particles, in the event a coagulation comprising an uneven mixture of the plurality of powders and/or particles is admixed into the charge of the vessel, the paddle mixer merely mixes the coagulation in its intact form with the remainder of the charge, and thus cannot prepare an even mixture of powders and/or particles in the sense of the initial primary powder/particle level because the coagulation cannot be crushed into levels of powder/particle diameters which the plurality of powders and/or particles originally exhibited.
It is therefore a first object of the invention to provide an apparatus for the precise treatment of powder and/or particle which is capable of efficiently manufacturing grains of a uniform grain diameter and which allows a scale-up for its use as a batch granulator of the agitation type. It is a second object of the invention to provide an apparatus of the above type which can be operated as a continuous precision granulator capable of continuously manufacturing grains having a uniform grain diameter and having differential specific gravities between an outer shell and an inner core thereof. It is a third object of the invention to provide an apparatus of the above type which can be operated as a continuous precision granulator capable of continuously manufacturing grains having a uniform grain diameter and having an even overall specific gravity. Finally, it is a fourth object of the invention to provide an apparatus of the above type which can be operated as a mixer capable of continuously manufacturing mixtures of grains, each grain representing an even mixture of primary level powders/particles.